The present invention relates to a method of and to an apparatus for making a continuous filler of fibrous material, particularly a tobacco filler which is ready to be draped into a web of cigarette paper or the like to form with the web a continuous tobacco-containing rod.
The invention will be described with reference to the making of a filler which can be converted into a portion of a cigarette rod. However, the method and apparatus of the present invention can be utilized with equal or with similar advantage in connection with the making of other types of rod-shaped articles of the tobacco processing industry such as cigarillos, cigars and filter rod section.
Modern cigarette making machines are equipped with distributors which deliver a continuous shower of fibrous material (such as fragments of tobacco leaves, fragments of reconstituted tobacco and/or fragments of substitute tobacco) onto a driven endless air-permeable belt conveyor travelling along a suction chamber so that the conveyor attracts the fragments and converts successive increments of the shower into a continuous stream containing a surplus of fibrous material. The surplus is removed by a suitable trimming or equalizing device so that the stream is converted into a substantially rod-shaped filler which is draped into cigarette paper or other suitable wrapping material in a so-called sizing part. The resulting cigarette rod is severed at predetermined intervals so as to yield a series of plain cigarettes of unit length or multiple unit length. The cigarettes can be advanced to storage, to a packing machine or to a filter tipping machine. Cigarette rod making machines of the above outlined type are manufactured by the assignee of the present application and are known as PROTOS.
That stretch or reach of the endless air-permeable conveyor which intercepts the shower of fibrous material is normally flat so that the stream which grows on the conveyor has a flat side or surface abutting the adjacent reach of the conveyor. The intercepting reach of the conveyor is normally located at the bottom of a tobacco channel wherein the stream must travel along stationary walls with attendant generation of friction which can interfere with predictable transport of the stream toward the surplus removing station. It has been found that the friction between the stationary walls of the tobacco channel and the adjacent sides or surfaces of the tobacco stream can interfere with predictable transport of the stream, even if the transporting or conveying unit including the air-permeable conveyor has a suction chamber which attracts the stream to one side of the belt conveyor with a substantial force. Additional problems arise when the thus formed stream enters the sizing part wherein the stream having a polygonal cross-sectional outline must be converted into a rod-like filler having a circular or substantially circular cross-sectional outline. As a rule, the stream which advances beyond the trimming or equalizing station has a rectangular or square cross-sectional outline. This means that the customary garniture tape, which is an element of the sizing part and advances the trimmed or equalized stream and the web of wrapping material through the draping station, must subject the trimmed stream to pronounced deforming stresses in order to eliminate the corners between the sides of the polygon during conversion of the freshly trimmed stream into a rod-like filler. Friction between the sizing part and the freshly trimmed stream, as well as between the sizing part and the web of cigarette paper is often sufficiently pronounced to entail a jamming at the inlet to the sizing part with resulting substantial losses in output. A modern cigarette maker turns out up to and in excess of 8000 plain cigarettes per minute.
The trimming or equalizing device of a conventional cigarette rod making machine normally comprises two rotary disc-shaped knives which are disposed at a variable distance from the stream-carrying reach of the air-permeable conveyor. The peripheries of the knives contact each other in a central longitudinal symmetry plane of the path which is defined by the stream-attracting and advancing reach of the belt conveyor. The plane of the knives is normal to the aforementioned symmetry lane and is parallel to the plane of the normally flat stream-attracting reach of the belt conveyor. The knives cooperate with the lateral walls of the tobacco channel and with the flat reach of the belt conveyor to impart to the trimmed stream a substantially square or a substantially rectangular cross-sectional outline. In other words, the outline of the freshly trimmed stream deviates considerably from the outline of the rod-like filler which issues from the sizing part of the cigarette rod making machine. Even minor accumulations of fibrous material and/or wrapping material at the inlet of the sizing part necessitate long-lasting interruptions of operation of the cigarette rod-making machine. This often necessitates an interruption of the operation of other machine or machines which are operatively connected with the cigarette rod making machine, such as a packing machine, a filter tipping machine and a filter rod making machine.